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Earth and Mars may have shared seeds of life

The following article published on phys.org, explores this question with SETI Institute senior research scientist Nathalie Cabrol.

Could Mars, of all places, be the place to look for early life on Earth?

It's an intriguing thought and one that astrobiologists take seriously as they consider the conditions during the early days of Solar System when both planets experienced frequent bombardments by asteroids and comets that resulted in debris exchange between one body and the other.

"We might be able to find evidence of our own origin in the most unlikely place, and this place is Mars," planetary scientist Nathalie Cabrol of the SETI institute said in a TED Talk in April 2015.

Cabrol studies life in extreme conditions on Earth with the hope that her research might help improve the search for signs of life on the Red Planet.

"We can go to Mars and try to find traces of our own origin. Mars may hold that secret for us," she said. "This is why Mars is so special to us."

'Throwing rocks'

Mars orbits an average of 140 million miles (225 million kilometers) from Earth and has a similar size and composition. During the period of the Late Heavy Bombardment, about 3.8 billion to 4 billion years ago, the planets were pummeled with asteroids and comets, which may have also provided the water to much of the Earth's oceans. Earth and Mars were, in a sense, connected to each other by the violence of this era.

"Earth and Mars kept throwing rocks at each other for a very long time," Cabrol said.

If life spawned on one planet, it could have clung to one or more of these samples and traveled to the other, a process scientists call panspermia. But if early Earth life did make it to Mars, it would have needed a hospitable arrival.

Today the planet is bleak and barren, resembling the Earth's most desolate deserts. With its thin atmosphere and almost completely waterless surface, any life that landed on Mars today would have a difficult time taking hold. But in the past, when the rocks were flying, Mars likely boasted a more habitable environment.

"At the time when life appeared on the Earth, Mars did have an ocean, it had volcanoes, it had lakes, and it had deltas," Cabrol said.

Yet unlike Earth, the Red Planet quickly lost its hold on habitability.